Refractory-metal body scarfing pneumatic powder dispensing apparatus



y 1956 F. M. MOESINGER, JR 2,743,964

REFRACTORY-METAL BODY SCARFING PNEUMATIC POWDER DISPENSING APPARATUS Original Filed April 18, 1950 3 Sheets-Sheet 1 IPIVENTOR FRED MO ESINGER ,JR.

y 1956 F. M. MOESINGER, JR 2,743,964

REFRACTORY-METAL BODY SCARFING PNEUMATIC POWDER DISPENSING APPARATUS Original Filed April 18, 1950 3 Sheets-Sheet 2 wwlv INVENTOR FRED MOESINGER,JR.

'ATYTORNEY ay 1, 1956 F. M. MOESINGER, JR 2,743,964

REFRACTORY-METAL BODY SCARFING PNEUMATIC POWDER DISPENSING APPARATUS 1 Filed April 18, 1950 3 Sheets-Sheet 5 igina POWDER NOZZLE PREHEAT Z4 WORK 4 INVENTOR FRED MOESINGER,JR.

' ATTORNEY REFRACTORY-NIETAL BODY SCARFlN G PNEU- MATIC POWDER DISPENSING APPARATUS Fred Moesinger, Jr., Morristown, N.J., assignor, by mesne assignments, to Union Carbide and Carbon Corpora- Iron, a corporation of New York Original application April 18, 1950, Serial No. 156,652,

now Patent No. 2,622,048, dated December 16, 1952.

5 Claims. (Cl. 302-53) This invention relates to powder dispensers, and more particularly to adjustable combined suction and pressure pneumatic fluid current powder conveyors for supplying an external relatively large flat stream of powder to a thermochemical scarfing reaction zone.

The present application is a division of my application Serial No. 156,652, filed April 18, 1950, for External Powder Scarfing Process, Product and Apparatus, now Patent No. 2,622,048 December 16, 1952.

In prior attempts to thermochemically scarf stainless steel with the aid of powdered iron, the latter was fed to the reaction zone internally, i. e., along with the scarfing oxygen stream. When internal powder feed equipment was used for scarfing stainless steel slabs, the process was expensive, and the surface quality of products rolled from scarfed slabs was not satisfactory in that a type of defect called a shiner was found to have frequent occurrence upon the rolled scarfed product. A shiner is a slightly depressed area of higher reflectivity with substantially the same composition as the base material. It is believed that heavy scale rich in admixed iron and possibly covering a metallic deposit on the plate itself is rolled into intimate contact with the underlying metal, thereby protecting it from furnace gases and air. Upon pickling, the thin rolled-in, metallic-scale layer is removed, exposing the protected Zone which is the shiner. Thus, it was necessary to mechanically grind the resulting surface in order to avoid undesirable shiners in the final product, thereby considerably increasing the cost. Also, such scarfing involved critical process factors; such as critical powder feed rate, and the resulting cut contours were not subject to satisfactory predetermined control.

In scarfing with an internally fed stream of powder in the past, such stream was usually round. As a result, a relatively deep groove was formed in each scarfing pass, so that it was necessary to subsequently remove considerable metal, which was expensive, in order to obtain a desired relatively fiat, scarfed surface. This trouble was accentuated due to the fact that the edges of borders of the groove were uneven, which was highly objectionable. In attempting to scarf with parallel streams of'scarfing oxygen containing internally fed powder, in one pass, the adjacent streams interfered with one another, and the resulting scarfed surface had fused powder globules on the ridges between the grooves or cuts, which made the product obviously unacceptable fo'rsubsequent rolling.

Another difiiculty with prior attempts to scarf stainless steel was due to inherent limitations in the available powder dispensing equipment. Control of the powder flow was restricted to a critical range. Furthermore, a single bleeder valve was used to adjust both the powder carrier gas back-pressure and the carrier .gas powder-.

injector pressure, which objectionably restricted the range of adjustment. The control was critical and the powder flow was non-uniform and limited in quantity.

Also, prior to the invention, powder distribution across a single or a multiple stream scarfing cut was non-uniform,

2,143,964 Patented May 1, 1956 2 due to the inherent concentration of the powder in the center of a single round stream, as well as non-uniform blending of the powder in adjacent streams.

Prior to the present invention, therefore, it was necessary to mechanically grind or chip stainless steel slabs, for example, to condition the surface for subsequent treatment. This was expensive, slow, and not entirely satisfactory for all grades of stainless steel. Prior attempts to thermochemically scarf stainless steel shapes were even more expensive.

The main object of this invention, therefore, is to provide an improved process which overcomes such problems. Another object of the invention is to provide apparatus for dispensing powdered solid fuel, which is eflicient and effective; substantially increasing the speed of scarfing while, at the same time, considerably reducing theconsumption of powder. Another object is to provide an improved powder dispenser which can be accurately adjusted over a relatively wide range. A further object is to provide means for discharging a relatively flat stream of powder in which the powder is substantially uniformly distributed thereacross. A still further object is to provide an improved semi-finished, stainless steel product.

According to the invention of my application Serial No. 156,652 there is provided a novel process for thermochemically scarfing hard-to-scarf metal work with the aid of powdered solid fuel, which comprises applying a relatively flat stream of commercially pure oxygen against the work surface at an acute dihedral angle, applying preheat to the work adjacent such oxygen stream; directing at least one separate, relatively flat stream of a suitable carrier gas containing relatively fine powdered solid fuel toward such oxygen stream at an acute dihedral angle therewith, at a lower velocity than that of the oxygen stream, so that the powder merges with the leading fringe only of the oxygen stream on the way of the latter toward the Work; and relatively moving the work and such streams along the path to be scarfed. The powdered solid fuel is uniformly distributed across the relatively flat carriergas stream, but does not enter into the main layer or core of the oxygen stream due to the higher velocity of the latter.

fuelis heated to ignition temperaturaandthe' sorheated particles then burn in the oxygen and liberate energy in the form of heat. Such liberated energy heats the metal being scarfed and the burningpowder attacks such metal,

raising the temperature and lowering the melting pointof the surface material. As a result, the subsequent-core of pure oxygen efliciently and effectively attacks 'the metal chemically and physically, removing a portionof the work surface. The reaction zone is then moved along a desired path to be scarfed at a relatively rapid rate,

so that the work is thermochemically desurfaced.

Scarfing passes up to six times wider. than was heretoforepossible are accomplished by the invention at:

scarfing speeds which are two to three times faster, and with 25 to per cent less powder consumption. Prothe combination of a blowpipe nozzle having a relatively flat continuous slot for discharging a stream of com-"j mercially pure oxygen against the work, and upper and lower rows of ports for discharging preheatingflame supporting jets of gas' adjacent such scarfing oxygen 0 stream, and a novel powdered solid fuelnozzle mounted adjacent the blowpipe nozzle. Such powderedsolid fuel As a result, substantially all of the powdered solid nozzle is. provided with. a relatively flat continuous slot for discharging the powdered solid fuel in a relatively flat stream of a suitable carrier gas separate from the scarfing oxygen, so that the powdered solid fuel first passes into the preheating flames, then against the scarfing oxygen-stream, and finally against the work being scarfed. Means are associated with the powdered solid fuel nozzle for assuring uniform transverse distribution of the powder in the carrier gas upon its discharge.

Accordingto the present invention there is also provided a process of forming a relatively flat or thin stream of relatively fine metallic powder in which the powder is substantially uniformly distributed across such stream, which comprises mixing the metallic powder with a stream ofcarrier gas, confining such stream to a longitudinal path, abruptly changing the direction of flow of the stream, confining the stream to a path of increasing width and decreasing thickness, and subsequently discharging the resulting fiat stream in which the powder is uniformly distributed transversely thereof, at an exit velocity of between 30 and 350 feet/second through a relatively narrow slot which is between 0.0150 and 0.0625 inch thick.

Adjustable powder dispenser means are also provided for supplying a selected amount of powdered solid fuel in a carrier gas, at a selected flow rate of the carrier gas, such. rate and amount being independently adjustable over relatively wide ranges.

In the drawing:

Fig. l is a view mainly in side elevation, parts being broken away and shown in section, of a scarfing machine illustrating the invention;

Fig. 2 is a View mainly in front elevation of the apparatus shown-in Fig. 1;

Fig. 3 is an enlarged fragmentary perspective view of the nozzle portion of such apparatus;

Fig. 4 is an enlarged fragmentary detail, mainly in cross-section, showing how the gas mixture is supplied to the preheating gas ports;

Fig. 5 is a flow diagram of the novel powder dispenser system of the invention;

Fig. 6 is a perspective view of a stainless steel body scarfed according to the invention; and

Fig. 7'is1 a diagram illustrating the relative dihedral angles of the work surface and streams in scarfing.

As shown in the drawings, the illustrated machine scarfing apparatus S is mounted on a suitable F above the path of the work W, such as a cold slab of stainless steel, to be scarfed. The apparatus S includes a relatively flat powder nozzle 10 mounted on a modified scarfing nozzle 12' of conventional construction. The nozzle 12 is preferably of the wide-continuous-slotted type having a relatively wide slot 14 for discharging a relatively fiat stream of commercially pure oxygen against the work W, as well as upper and lower rows of ports 16 and 18 for discharging preheating-flame supporting jets of premixed oxy-acetylene gas adjacent such scarfing oxygen stream. The burning gas jets merge into preheating flames 22 and 24 which extend above and below the oxygen stream 20, forming dihedral angles with the work surface 25.

Oxygen is supplied to the nozzle 12, for example, from a suitable source of oxygen under pressure, by way of a supply pipe 26, a manifold 28 and a battery of tubes 30. At the same time, a suitable combustible mixture of oxygen and acetylene, or other fuel gas, is supplied to the preheating flame ports 16 and 18 by way of gas pipes 32 which are connected to suitable gas mixers and supplies of oxygen and fuel gas under pressure.

The powder nozzle 10 is mounted by a suitable bracket 33 directly on the blowpipe nozzle 12, and comprises a metal base 34 and a metal cover 36 secured together by bolts 38; The base 34 and the cover 36 are provided with a channel, or mating channels, forming a slot 40 for discharginga suitable relatively flat powder-laden carrier gas stream 39, which can be any suitable gas, such as air, or nitrogen, or" oxygen, for example. The discharge face of the powder nozzle 10 is tapered and positioned on the blowpipe nozzle 12 so that slot 40 discharges the separate powder-laden carrier gas stream 39 from a fiat orifice 41 located directly above the frontupper edge of the nozzle 12. The powder-laden gas stream 39" forms-a dihedralangle with the oxygen stream 20, and with the work surface 25.

The upper and lower walls of the slot 40 diverge slightly upstream, and the upper end of the slot is in communication with the outlet end of a novel powder distributor 42 made of sheet-metal in the form of a fishtail which is supported in front of the oxygen manitold 28 by a bracket 44. The interior of the powder distributor 42 has side walls 46 which diverge in the direction of the powder flow, and front and rear walls 48 which gradually converge. in the direction of such flow.

The illustratedpowder distributor 42 isprovided at the upper end thereof with an angulated tubular inlet 50 for assisting in the proper distribution of powder transversely of the carrier gas stream. Such inlet 50 is connected by a hose 51 to a novel powder-laden carrier-gas supply system. As shown in Fig. 5, the powder-laden carrier-gas supply system includes a novel powder dispenser 52in the form of a gas-tight hopper containing a suitable supply of solid-fuel powder P, in this case relatively fine ferrous metalpowder. The powder dispenser 52 comprises a suitable cover 54 provided with a gas pressure relief valve 56. The dispenser is supported by legs 58 and has a funnel-shaped bottom portion 60 which guides the powder P toward an outlet from which depends a flexible tube 62 provided with a pinch-type shut-off valve 64 which is connected to a diaphragm 66 by a rod 68.

The powder supply system is designed so that the powder flow from the dispenser 52 through the outlet 62 and valve 64, can be adjusted over a relatively wide range independently of the carrier or transporting gas flow from the dispenser outlet to the powder nozzle 10, so that the rate of the gas flow alsocan be adjusted over a relatively wide. range, and the powder hose 51 and the powder nozzle can be purged of powder with the gas, when the powder flow is turned off by closure of the valve 64. The powder flow is initiated or arrested by manipulating a remotely located switch- 72 in an electric supply circuit 74. containing a solenoid 76 which operates a three-way valve 78 in a. compressed air line 80 which is connected by an inlet pipe 82 to a suitable source of air under pressure. The outlet of the line 80 is connected to one side of the diaphragm 66. In one position of the valve 78 air under pressure is supplied to the diaphragm 66, causing the valve 64 to close; while in its other position the valve 78 shuts off the air inlet pipe 82 and connects the pipe 80 to an air exhaust pipe 84, causing thevalve 64 to open.

The. carrier gas from a suitable source of supply under pressure, enters the system through an inlet pipe 86 and is split into two unequal streams by a T-fitting 88. The smaller stream flows through a pipe 90 containing a gas pressure regulator 92, the outlet end of the pipe 90 being connected to the interior of the dispenser 52 above the powder P. Here the carrier gas exerts a positive pressure on the top of the powder P. The main carrier gas stream, however, flows through a suitable pipe 93 containing a gas pressure regulator 94 and a critical orifice flowmeter 96 which, with regulator 94, controls the main powder transporting gas stream finally entering a chamber 98 on the downstream side of the powder dispenser 52.

The powder flow rateis controlled by the size of the orifice or outlet 62 at the bottom of the dispenser, and

the gas pressure differential across such orifice. The flow rate in pounds per minute is a substantially straight line function of this differential pressure which is indicated by a differential pressure gauge 100 in a pipe 102 having one end connected to the pipe 90 and other to the pipe 93. Gauge 100 measures the difference in pres-.

sure between space PH above powder P, and space PD in chamber 98. The pipe 102 is also provided with a hopper inlet pressure gauge 104 and a discharge pressure gauge 106. Actual powder flow may be determined by consulting a chart or curve based on the straight line function of the differential pressure.

Thus, eachgas stream is controlled independently of the other. In this way the flow of carrier gas can be accurately adjusted without changingthe flow of pressurizing gas to the hopper, and vice versa. This permits adjustment, at will, of the density of the powder-air mixture leaving the dispenser and also adjustment of the velocity of the powder, giving greater latitude to the control of all important variables.

In operation, the powder leaves the dispenser 52 through orifice 62, passing through the pinch-type diaphragm-operated valve 64the on-off operation of which is controlled by the solenoid operated air valve 78. Leaving valve 64 the powder is picked up in chamber 98 by the carrier gas stream and enters, through the funnelled bottom outlet 107 thereof, the hose 51 leading to the fishtail powder distributor 42.

As pointed out above, the powder distributor 42 is provided with a tubular shaped inlet 50 which is angulated with respect to the distributor, so that the powder flow impinges atan abrupt angle against the back wall of .the fan-shaped body proper of such distributor. This change of direction plus the flattening out of the passage, distributes the powder uniformly across the confined stream. The distributor contains a fan-shaped interior approach section terminating in an exit slot 110 which is in communication with the inlet end of the slot 40 in the powder nozzle 10, the parts being secured together in gas-tight relation by an escutcheon 112. The powder nozzle which receives the powder which has been uniformly spread out by the action of the distributor 42 has downwardly convergent upper and lower walls in the slot 40 which discharges. the powder through the exit orifice 41 which, in the illustrated apparatus, is about 0.03 inch by 6.00 inches in size, and then through the upper preheating flames 22 of the scarfing nozzle 12. In the present example the scarfing nozzle 12 is provided with a scarfing oxygen slot 14 which is also about 6.00 inches wide.

The following table discloses typical performance data for 6-inch and 2-inch wide scarfing equipment.

PERFORMANCE DATA Nozzle Size (5-inch Unit 2-inch Unit Cut Depth ..1'nches.. .125 250 .05 10 Powder Feed Rate, lb./rnin 9.0 7.0 2. 5 2. 5 Powder Consumption, Lb./Sq. Ft--. 0. 69 0. 70 0.38 0. 74 Air Flow, Cu. Ft. Hr 1, 500 1, 500 500 500 Air Velocity (Discharge), Ft./Sec. 350 350 350 350 The following table discloses ratios for different units.

In the illustrated apparatus (6 unit), at an exit velocity of between 30 and 350 feet/second, the impingement angle of the powder stream on the preheating flames, i. e., the optimum included angle between the powder nozzle 10 and the continuous slotted oxygen nozzle 12 is about 40, when the exit velocity of the latter is between 500 and 850 feet/second. In other words, the slotted scarfing nozzle makes an optimum dihedral angle of 30 with the top surface of the work, and the powder nozzle makes an optimum dihedral angle of 70 with the top surface of the work.

The following table, when considered in connection with Fig. 7 discloses optimum nozzle arrangements in connection with actual performance data of various units.

OPTIMUM DIHEDRAL ANGLES AND PERFORMANCE DATA The following tables illustrate the composition and size of an example of the iron powder which has been used succesfully according to this invention. Other examples can be found in Wagner 2,451,422.

CHEMICAL COMPOSITION Percent Free iron At least 85.00 Total carbon Not over .30 Residual material Balance PHYSICAL PROPERTIES Free from any contaminating materials as, for example, wooden splinters, fibers, or non-ferrous alloys of brass and bronze.

Screen size Percent on 200 mesh 25 200 on 325 mesh 25 325 50 Scarfing speeds (i. e., relative movement between the work and the scarfing unit) obtained according to this invention, that is to say ,15-50 feet/minute, are up to six times faster than when using a prior single nozzle powder scarfing machine with internal powder feeding. This is accomplished with 25 to 75% less powder consumption per unit of scarfed surface. The invention also eliminates shiners in stainless steel sheets rolled from slabs scarfed with powder consisting essentially of iron, without mechanically grinding the scarfed surface before final rolling. The invention, furthermore, results in a surface of good quality in the as-scarfed condition, i. e., such that it may be rolled into a finished shape, requiring a minimum of additional conditioning.

The scale 114 that remains adhering to the base metal 116 of the work W, Fig. 6, has a very high degree of oxidation. There is practically no FeO, and substantially or mainly all of such scale is R304. The oxidation products are substantially free of admixed metal (particularly iron or iron-rich metallic compounds). The scale layer may be classified as light. When the base metal 116 is stainless steel, its surface is relatively free of slag and shows only a typical melted condition of the surface on the order of magnitude of 0.005 inch, or less, in thickness. The base metal also is substantially free of metallic particles, deposited on, or adhering to its surface.

The scale 114 adhering to the base metal 116 is not 7 tightly bonded; and has little tendency to adhere during subsequent heating, rolling. and processing. Further, the scale isquite uniform in distribution, composition and adherence, and is of such a nature that subsequent heating and rolling produces practically no tendency to force the scale 114 into intimate contact with the base metal 116'. Thus, the resulting product, when rolled, is free of shiners, the mechanical grinding step being entirely eliminated. Furthermore, this is accomplished with considerably less powder at a'much faster rate and substantially less cost than was possible prior to the invention.

I claim:

1. A powder dispenser including a closed powder hopper having a restricted powder outlet in the bottom thereof, a tube depending from such outlet, a powder shutotf valve associated with said tube between the hopper bottom outlet and the bottom of said depending tube, a closed powder pick-up chamber containing said depending tube, said pick-up chamber having a funnelled bottom with an outlet spaced below the tube, a gas-borne powder delivery hose connected to said pick-up chamber outlet, a powder-carrier gas supply pipe connected to said powder pick-up chamber, means for adjusting the pressureof such gas to pick up the powder from said depending tube and carry it through the outlet therebelow and on through said gas-borne powder delivery hose, a compressed gas supply pipe connected to said hopper above the powder therein, and means for adjusting the pressure of such compressed gas to force the powder from said hopper through its restricted powder outlet and the tube depending therefrom into said pick-up chamber.

2. A powder dispenser comprising a closed powder hopper having, a restricted powder outlet in the bottom thereof, a flexible tube depending from such outlet, a pinch-type powder shut-off valve associated with said tube between the hopper bottom outlet and the bottom of said depending tube, a closed powder pick-up chamber containing said depending tube, said pick-up chamber having a funnelled bottom with an outlet spaced below the tube, a gas-borne powder delivery hose connected to said pickup chamber outlet 21 powder-carrier gas supply pipe connected to said powder pick-up chamber, means for adjusting the pressure of such gas'to pickup the powder from said depending tube and carry it through the outlet therebelow and on through said gas-bornepowder. delivery hose, a. compressed gas supply pipe connected to said hopthe pressure of such compressed gas to force the powder from said hopper through its restricted powder outlet and the tube depending therefrom into said powder pick-up chamber.

3. A powder dispenser comprising a closed powder hopper having a restricted powder outlet in the bottom thereof, a closed powder pick-up chamber having a funnelled bottom with an outlet spaced below such hopper outlet, a-gas-borne powder delivery hose connected to said pick-up chamber outlet, a powder-carrier gas supply pipe connected to said powder pick-up chamber, means for adjusting, the pressure of such gas to pick up powder from said hopper outlet and carry it through the outlet therebelow on through said gas-borne powder delivery hose, a compressed gas supply pipe connected to said hopper above the powder therein, means for adjusting the pressure of such compressed gas to force the powder from said hopper through its restricted powder outlet into said powder pickup chamber, and a differential pressure gauge connected across such pipes.

4.. A powder dispenser as claimed in claim 2 in which the pinch-type powder shut-off valve is provided with an operating rod' passing through said closed chamber, a diaphragm is mounted on said rod for operating said valve, and said diaphragm is provided with pneumatic operating means.

5. A powder dispenser as claimed in claim 2 in which the pinch-type powder shut-off valve is operated by pneumatic means, and a remote controlled electrically operated valve is provided for said pneumatic means.

References Cited in the file of this patent UNITED STATES PATENTS 847,270 Wise Mar. 12, 1907 851,668 James Apr. 30, 1907 864,471 Kelley Aug. 27, 1907 951,754 Buzzell Mar. 8, 1910 1,100,992 Sallee June 23, 1914 1,627,926 Payzant May 10, 1927 2,283,932 Jones May 26, 1942 2,284,574 Jacobson May 26, 1942 2,296,309 Reeves Sept. 22, 1942 2,327,337 Burch et al Aug. 24, 1943 2,536,201 Meincke et al. Jan. 2, 1951 

1. A POWDER DISPENSER INCLUDING A CLOSED POWDER HOPPER HAVING A RESTRICTED POWDER OUTLET IN THE BOTTOM THEREOF, A TUBE DEPENDING FROM SUCH OUTLET, A POWDER SHUTOFF VALVE ASSOCIATED WITH SAID TUBE BETWEEN THE HOPPER BOTTOM OUTLET AND THE BOTTOM OF SAID DEPENDING TUBE, A CLOSED POWDER PICK-UP CHAMBER CONTAINING SAID DEPENDING TUBE, SAID PICK-UP CHAMBER HAVING A FUNNELLED BOTTOM WITH AN OUTLET SPACED BELOW THE TUBE, A GAS-BORNE POWDER DELIVERY HOSE CONNECTED TO SAID PICK-UP CHAMBER OUTLET, A POWDER-CARRIER GAS SUPPLY PIPE CONNECTED TO SAID POWDER PICK-UP CHAMBER, MEANS FOR ADJUSTING THE PRESSURE OF SUCH GAS TO PICK UP THE POWDER FROM SAID DEPENDING TUBE AND 